1. Field of Art
This invention relates to the improvement of the rear steering axle on an agricultural combine. More specifically, the invention is an offset kingpin for the rear steering axle on a combine.
2. Description of Prior Art
Mechanical harvesting of grain has taken place for decades. However, efforts continue in the attempt to make harvesting operations more efficient and effective. A combine harvester generally includes a header, which cuts the crop. The header then moves the cut crop into a feeder house. The feeder house lifts the cut crop into the threshing, separation and cleaning areas of the combine. The grain is separated from the stalk by a rotor or cylinder threshing system. The grain is then separated and moved and stored in a grain tank. The chaff and trash are deposited from the rear of the combine. The grain stored in the grain tank is eventually discharged through a grain tank unload tube. An operator usually runs these various operations from a glass-enclosed cab. Typically, the cab is located above and behind the header and feederhouse. There are a variety of agricultural combine harvesters and their operations are well known in the art. For examples of such harvesters reference U.S. Pat. No. 4,846,198 which illustrates the conventional and twin rotor threshing and separating systems of a harvester as well as other major systems of the harvester. See also the New Holland Super Conventional Combines TX.TM. 66, TX.TM. 68, the New Holland TWIN ROTOR.RTM. combines TR.RTM. 89 and TR.RTM.99 for examples of existing conventional and twin rotor harvesters. U.S. Pat. No. 4,332,262 also illustrates the primary systems of a conventional harvester. For further details regarding various agricultural harvester systems review U.S. Pat. Nos. 4,522,553, 4,800,711, 4,866,920, 4,907,402, 4,967,544 and 5,155,984. See also the New Holland corn head model 996 and the New Holland grain belt header model 994 for details regarding headers.
The previously indicated, the combine moves across a field to harvest crop. Two pairs of wheels supports the combine. Typically, larger front wheels are driven and the smaller rear (optionally driven) wheels are attached to a steerable rear axle. As with most land vehicles, the wheels are steered. Specifically, the inner tire (the tire closest to the center of the turn) is steered through a greater angle than the outer tire. Presently there are several difficulties incumbent with this approach on an agricultural combine. Because of the shielding and chaff spreader the rear tires contact the shielding. This limits the turning radius available for the rear tires. Furthermore, as agricultural combines have grown in size and complexity, so has the requirement for larger tires. This further decreases the clearance between the tires and shielding. Many two wheel drive tractors and automobiles have used spindles which trail their kingpins. This aids highway steering stability. With a front steering axle common on these vehicles, this exaggerates the inner and outer tire chassis clearance problems. However, the tire width and chassis clearance can be modified to avoid this issue on such vehicles. This option is not viable on a rear steering axle on an agricultural combine. There is equipment that must be placed behind and next to the rear wheels in order to have a successful farming operation. The prior art illustrates these drawbacks. U.S. Pat. No. 2,193,752 illustrates a steering mechanism on a front axle of a motor vehicle. U.S. Pat. No. 2,256,366 again illustrates an offset kingpin in the front axle of a vehicle. U.S. Pat. No. 2,566,565 discloses a vehicle steering knuckle mechanism for effecting sharp turns. Again, the disclosure reveals a front axle of relatively simply pull-type vehicle.
A rear steering axle that would improve the turning radius of an agricultural combine while not diminishing the clearance between the rear tires and the combine side shielding would be a great improvement. An invention that could resolve these issues would represent an improvement to the art.